Key matrix



FIG. 1 is a front, top and right side perspective view of a key matrix showing our new design;

FIG. 2 is a top elevational view thereof;

FIG. 3 is a front plan view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a rear plan view thereof. 

The ornamental design for a "key matrix", as shown and described. 